Anxiety and depressive disorders are highly prevalent, costly, and debilitating, representing a serious public health concern. Although time-limited, efficacious interventions have been developed for these common conditions, these treatment protocols often require more sessions than patients in community practice typically attend. Thus, it is critical to increase the efficiency of our interventions such that the skills that drive therapeutic change are presented as early as possible. Transdiagnostic interventions designed to directly target core processes implicated in the development of a range of conditions may increase treatment efficiency by simultaneously leading to improvements across comorbid conditions. However, transdiagnostic treatments contain multiple treatment elements (modules) and it is possible that some skills may be better suited for target engagement based on each patient's clinical presentation; prioritization of those modules may lead to earlier and more robust symptom improvements. Unfortunately, we lack empirical evidence to guide treatment planning so that care is personalized to the patient's unique strengths and weaknesses. Additionally, evidence-based decision rules regarding when to terminate treatment based on promising early markers of improvement, rather than complete symptom remission, may also improve treatment efficiency, making care available to a greater number of individuals. It is also possible that engagement of core processes may serve as an early indication that a sufficient dose of treatment has been received, aiding decisions about when to discontinue care. The proposed study will determine the feasibility, tolerability, and acceptability of a study that tests: 1) personalized treatment delivery (i.e., module sequencing and treatment discontinuation timing) aimed at increasing the efficiency of care, and 2) the research protocol designed to evaluate the effects of this personalized care. A sample of 60 participants with heterogeneous anxiety disorders (and comorbid conditions, including depression) will be enrolled in a pilot sequential multiple assignment randomized trial (SMART). Patients will be randomly assigned to one of three sequencing conditions: transdiagnostic treatment administered in its standard module order, module sequences that prioritize capitalizing on relative strengths, and module sequences that prioritize compensating for relative weaknesses. Next, after 6 sessions, participants will be randomly assigned to either continue or discontinue treatment to evaluate post-treatment change at varying levels of target engagement. This proposal will enable us to 1) test the feasibility, acceptability, and tolerability of the research protocol, treatment sequencing conditions, and early treatment discontinuation, 2) determine whether a preliminary signal that capitalization or compensation module sequencing improves treatment efficiency exists, and 3) explore preliminary associations between core process engagement at treatment discontinuation and later symptom improvement. The proposed study, and the subsequent research it will support, will inform evidence-based decision rules to make existing treatments more efficient, ultimately reducing patient costs and increasing the mental health service system's capacity to address the needs of more individuals.